Pressure energy exchanger



P. KOLLSMAN 2,591,441

PRESSURE ENERGY EXCHANGER Filed Feb. 10, 1949 PROCESS/N6 UNIT {I t I 42 I 25 21 w [4 J /2 35 I, 5 4/ R v INVENTUR. pflBgL. KOL-LSMHN ATTORNEY Patented Apr. 1, 1952 UNITED STATES PATENT OFFICE PRESSURE ENERGY EXCHANGER Paul Kol lsman, New York, N. Y.

Application February 10, 1949, Serial No. 75,610

6 Claims.

The invention provides a method of an apparatus for the direct recovery of the pressure energy imparted to fluids before or during processing.

Many processes, such as chemical processes, distillation processes, are carried out within a range of elevated pressures, and a considerable amount of mechanical energy is generally required for raising the pressure of the fluid to the pressure at which the process is carried out. If the processed fluid is discharged by simple decompression, that is by flow through a throttling passage, the pressure energy is lost. If, on the other hand, the fluid is discharged by conducting it through suitable prime movers, for example, turbines, to extract the pressure energy from the fluid, a certain percentage of the mechanical energy originally expended can be recovered. However, this form of recovery of pressure energy is not very emcient, since it is an indirect way of recovery in which considerable losses occur by reason of limited efficiency of the several mechanical units employed in the recovery. Assuming, for example, that the processed fluid is conducted through a turbine and that the turbine is used to drive some unit of the processing equipment, perhaps contributes a portion of the mechanical power for driving the pump, it is easily seen that the net recovery of energy is reduced by the losses occurring in the turbine, in the transmission of mechanical power, and in the pump.

Furthermore, the indirect form of recovery is often not practicable, for example, where the available volume of processed fluid is too small to drive a turbine of standard dimensions and design.

The invention proposes a method of direct recovery of pressure energy which offers numerous advantages over the indirect form of recovery in that no turbines or similar devices are required for converting pressure energy into mechanical energy. The invention provides for substantially complete recovery of the pressure energy and permits the recovery unit to be constructed of relatively simple elements and of relatively small size.

The various objects, features, and advantages of this invention will appear more fully from the detailed description which follows, accompanied by drawings showing, for the purpose of illustration, a preferred form of apparatus for carrying out the novel method. The invention also consists in the certain new and original steps and combination of steps as well as new and original 2 features of construction and combination of elements hereinafter set forth and claimed.

Although the characteristic features of thisinvention which are believed to be novel will be particularly pointed out in the claims appended hereto, the invention itself, its objects and advantages, and the manner in which it may be carried out may be better understood by referring to the following description taken in connection with the accompanying drawing forming a part of it in which the figure is an illustration, partly diagrammatic, and partly in section, of an improved form of apparatus for the direct recovery of pressure energy from fluids processed under high pressure.

In the following description and in the claims various details will be identified by specific names for convenience. The names, however, are intended to be as generic in their application as the art will permit.

In the drawing accompanying, and forming part of, this-specification, certain specific disclosure of the invention is made for the purpose of explanation of broader aspects of the invention, but it is understood that details may be modified in various respects without departure from the broad principles of the invention and that the invention may be applied to other structures than the ones shown.

For reasons'of simplicity and convenient readability of the drawing the apparatus is not shown to scale, and particularly the wall thicknesses of the several elements are shown without regard to their actual dimensions, it being understood that the portions of the ducts and thewa-lls sustaining full operating pressure must be constructed sufliciently heavy to withstand the operating pressure. H 7

Since the specific nature of the process to which the fluid is subjected at elevated pressures is immaterial, the processing unit is shown only diagrammatically as. having an inlet duct and an outlet duct.

A hereinbefore mentioned, the process to which the fluid is subjected may be a chemical process, may be a still operating at high pressures, for example, a still operating at substantially the critical pressure and the critical temperature, or it may be any other form of apparatus.

Referring now briefly to some characteristic steps of the method of recovering pressure energy, a volume of fluid to be processed is first confined at substantially atmospheric pressure. Then a second volume of processed fluid is compressed to the processing pressure, this'second volume iidl h r' lcessing being smaller than the first volume and being in pressure transferring relationship with the first volume. The second volume, however, is separated from the first volume to prevent mixing of the two. Then communication is established between the second volume and'a supply of processed fluid under a pressure higher than the pressure of the first volume and simultaneously discharge of the first volume towards a processing point under processing pressure is permitted. This causes the first volume of fluid to decrease and the second volume to increase. Then both volumes are again confined. Then the second volume is decompressed and is discharged -a,t s ub-.

stantially atmospheric pressure. Simultaneous- 1y, communication is established between the first volume in the source of fluid to be processed and the volumetric relationship of the two volumes initially existin is reestablished.

The drawing illustrates; a simple form of pressure exchanger which extracts. pressure energy from a processed liquid and utilizes-the recovered pressure energy for compressing a corresponding volume of liquid to be .fed,into the processing unit.

The pressureexchanger basically comprises twochambers, an intake chamber and an. outlet chamber. These chambers are sealed from each other to prevent mixing of fluids contained therein, but are otherwisqin pressure exchanging communication or relationship. This is accomplished by providing a movable pressuretransferring but fluid separating means in. a passage through which both chambers communicate. This .movable pressure transferring meansmayassume a: number of convenient forms. It may beamechanical wall such as ,adiaphragm, a Sylphon or a floating piston. It mayalso be a fiuidbarrier, for: ekample, a charge of liquid such-asmercury oscillating back and forth in a duct.

For reasons, of simplicity a floating. piston I I is shown movable; within a cylinder. rod]; and. sealedat l4 and.

her 30. A discharge port 3| for the outlet chamber I1 is controlled by a discharge valve member 32 and theprocessed fluid leaves the apparatus through a low pressure duct 33.

A compressor is provided for periodically compressing and decompressing the fluid in the chambers l6 and I1. For reasons of simplicity the coinpressor is shown in the form of a piston 34 movable within a compressor cylinder 35 with respect to which it is sealed at 36. The piston is guided by a crosshead 37 and is operated through a con necting rod 38 from a power crankshaft 39 driven by a motor 40.

The piston 34 has a valve operating stem 4| on it adapted to bear against the inlet valve member to lift the valve member off its seat against thegforce of the spring 42 tending to maintain the inletvalve closed.

12 guided by a.- .I5.- This floating pistonneed notfbe eirceedingly strong since as A will appear from. the following description,- it i rarely everlsustainsthe full operating pressure. 1

The floating piston .ll divides. the cylinderpaceinto an intake chamber. chamber I1.

an intake port [8 controlled by an intake check [6. and an outlet The intake chamber has two ports,-

valve I9 andan outlet port 29 icontrolled by an outlet'check valve 2| The intake. port l8 lies at theendofa rawfluid feed duct22 withinwhich-ja low--pressured. Ph ip. 2 id .f dm a er y 2hen e is shown as a tank 2 The outlet check valve .lies at the 1 a high pressure feed duct 25 leadingto the proc- 3 1 is arranged which supplies rawsource 'of supply to ,the pressure; This source' of fluid supply entrance ofessing ujnitjt'fi. A low. pressure circulatingr'pump 21 may b provided in the highpressure feed; duct"- 7 for circulating the fluid through the processing unit. Thi s p ump is pressure. .-'Ihe pressure difni al h we be sm ua ineea.

built, strong enough to with'- produced. by this pump can be no larger than is suflicient to overcome the flu d flow resistanceencountered by the fluid in its ber l6 through theprocessing unit 26 to the outlet chamber l 'l.

passage from the-intake cham- I Processed iliuid: reaches the pressure exchanger 7;

through a high pressure, duct 8 from the process ingurlitand. enters'theoutlet chamber 1 Ithfbushf an inlet port 12g controlled by an inlet valvemem chambersil'l audit; of the valvemperating stem 4 pump"?! which overcomes the to fill the'outlet" floating-'tpistondl to the right. 5

The discharge valve member 32 is similarly operated by a valve stem 43 supported by a crosshead ltfloperated from the crankshaft througha connecting rod 45. The crank 46 operating the compressor piston is offset with respect to the crank 41 operating the discharge valve member 32; A ;spring 48 bears against the'dischargeivalve member132 and tends to maintain the discharge valve closed.

Theadevice: operates as follows n It mayybe assumed that at the start of the operation all the passages and chambers of the processing unit and of the pressure exchanger are fllledwith fluid and that the processing unit is under elevated processing pressure.

It may further be assumed that all the elements of the apparatus are in the position inwhich they areshown and-tliat the motor 40 moves the cross v head-3'1 in an upward direction so that the piston l 34 compresses the fluid in the chamber I]. In 4 theaposition shownthe'piston has raised the .pressureinside the outlet chamber IT to the operating pressure' existing'in the processing unitlf Theypressure intheoutlet chamber II'is tr'ansff mitted'xto :thin'take chamber l6" through the floating piston H-.- V H 7 During the-compression of the volume of 'fluidf in theoutletchainber I! the'floating pistonj l l 1 moves from Litsleft end position. This movement A is slight if the fluid to beprocessed is a liquid,fbult i a certain amount of-rnovement takes place due 7 toithelimited compressibility of liquids, par'ticu-T f larly if :the' operating pressure is high, for'fex-f ample, of the order of three thousand poundsper squareinchlemployed in some distillation unitsl In? the.i:pOSitiC$llSh0Wn' the pressure in thei, P ure exc an r approximatelyfequal-to the-pressure" in the pro 1 essing unit, but the chambers of the pressurej" exchanger remain-sealed at theintake port lll by the-check valve I'd-at the outletport 20 bythe; .checlcvalve 2I, -at the-inlet'p'ort' 29 by the valve 11; memberfiflyand 'at thedischar'g'e port 31' bythe valve:member"32.

Thus-:wh'en the piston 34 rises further, :the', l engages the inlet tvalv" 30 and lifts-it off its seat; thereby causing proc essed fluid to flow from the processing unit 2g through the high pressure duct"28. Thisflow occurs because of the action of the circulating flow resistance o f theinstallationincludingthe frictionalresistance encountered-by the floatingpiston'l'lii Thepump z'l their causes the-processed fluid chamber f1 thereby moving ,th

causes anequal volume of unprocessed fluid to enter the processing unit through the outlet port,

20 past the check valve 2|.

At the time the outlet chamber I1 is filled and the intake chamber I6 is empty, the valve operat-. ing stem 4| has reached a position in which the valve member 30 is about to close the inlet port 29. The compressor piston 34 now retracts and causes the charge of fluid in both chambers of the pressure exchanger to be decompressed to substantially atmospheric pressure.

The energy available at the piston 34 during the decompression stroke is suitably transmitted to another compressor piston within the installation which passes through its compression stroke at this moment. Forthis reason the installation preferably comprises a series of individual pressure exchangers like the one shown connected in parallel to feed fluid to, and withdraw fluid from, the processing unit 26 at a substantially constant rate. Under such an arrangement the mechanical energy which actually has to be supplied by the motor 40 can be maintained relatively small. In fact the energy input by the motor need not be more than to compensate for actual friction and resistance losses in the system. units may be connected to the crank shaft to the left of the crank 41 where the crankshaft is shown broken off at 49.

After the operating stem 43 reaches the position in which it engages and opens the discharge valve member 32, processed fluid flows out through the low pressure discharge duct 33. The fluid is forced out of the pressure energy exchanger by action of the feed pump 23 which is now effective to lift the check valve l9 off its seat and feed raw fluid into the intake chamber 16. This causes the floating piston H to travel to the left whereby the volume of the outlet chamber I1 is reduced and a proportional amount of processed fluid is discharged.

Although it is desirable to provide for compression and decompression of the fluid within the chambers by a separate compressing and decompressing means, such as the piston shown at 34, the compression and decompressing means may be omitted.

In an installation, thus simplified in construction, the inlet valve member 30 as well as the discharge valve member 32 would be operated against the fully differential pressure and, as a result, a certain amount of energy would be lost by fluid friction at the valves. This loss is relatively small, of the order of 1 or 2 per cent. Approximately 98 per cent of the pressure energy would still be recovered by exchange between the volumes of processed liquid and the volumes of liquid to be processed. In the simplified construction somewhat greater valve wear would be experienced by reason of high velocities of flow occurring at the valves.

In large installations, however, operating under high pressures and handling large volumes of fluid, for example, installations for the conversion of salt water into fresh water the recovery of the 1 or 2 per cent of energy may amount to a sizable gain. For example, it requires 26,000 H. P. to compress one cubic meter of water per second to the critical pressure. In an installation handling one cubic meter per second approximately 500 to 1,000 H. P. could be saved by eliminating the throttling losses at the valves by provision of a separate device for compressing and decompressing the fluid in the energy exchanger prior to opening of the valves.

It thus appears that the pressure in the pressure Such additional pressure exchanger;

mospheric pressure or the pressure at which fluid is fed into the apparatus and is discharged and the full operating pressure of the processing unit.

It is quite apparent that the mechanical energy required for maintaining the apparatus in operation is low since the pressure energy is directly recovered. This flow of recovery is preferable, and more economical than, indirect recovery in which the processed fluid under pressure is used, for example, to drive turbine and a turbine is used to drive some other mechanical unit of the installation.

What is claimed is: I

1. A device for the recovery of pressure energy of fluids processed under high pressure in a processing system,the device comprising, an intake chamber having an intake port, and an outlet port leading to said system; intake valve means controlling said intake port; outlet valve means controlling said outlet port; an outlet chamber having an inlet port for admission of fluid from said system, and a discharge port; an inlet valve member controlling said inlet port; a discharge valve member controlling said discharge port; pressure equalizing means between said two chambers, including means for sealing fluid in one chamber with respect to fluid in the other chamber; means for periodically compressing and de compressing the fluid in one of said chambers; and means operable in timed relationship with said compressing and decompressing means for operating said inlet valve member and said discharge valve member.

2. A device for the recovery of pressure energy offluids processed under high pressure in a processing system, the device comprising, an intake chamber having an intake port, and an outlet port leading to said system; an intake check valve controlling said intake port; and outlet check valve controlling said outlet port; an outlet cham ber having an inlet port for admission of fluid from said system, and a discharge port; an inlet valve member controlling said inlet port; a discharge valve member controlling said discharge port; a movable pressure equalizing wall between said chambers sealing one chamber with respect to the other but permitting equalization of pressure therebetween; means for periodically compressing and decompressing the fluid in one of said chambers; and means operable in timed relationship with said compressing and decompressing means for operating said inlet valve member and said discharge valve member.

3. A device for the recovery of pressure energy of fluids processed under high pressure in a processing system, the device comprising a cylinder; a piston movable in said cylinder subdividing the cylinder into an intake chamber and an outlet chamber, said intake chamber having an intake port and an outlet port leading to said system, said outlet chamber having an inlet port for admission of fluid from said system, and a discharge port; an intake check valve controlling said intake port; an outlet check valve controlling said outlet port; an inlet valve member controlling said inlet port; a discharge valve member controlling said discharge port; means separate and distinct from said piston for periodically compressing and decompressing the fluid in said outlet chamber; and means operable in timed relationship with said compressing and decompressing means for operating said inlet valve member and said discharge member.

4. A device for the recovery of pressure energy port leading to said system; intakevalve 'r'ne'ans controlling said intake port; outlet lvalveQmea-ns 5 controlling said outlet port; an outlet chamber having an inlet portfor admission of fluid from l s 6. -A-device-for the recovery of pressure energy said system, and a dischargeport aniinlet valve member controlling said inlet, port; fa-Ldischarge I valve member controlling said discharge.."port; 10

a circulating pump in the passagelbetwe nis'aid 0utlet po rt and said inlet; port; which v passage includes the processing 'systemjsaidrpump lfeeding fluid towards said i nlet"port;gpressure equaliz its; means between. said two chambersfincludin '15 means for-sealingfiuicl in onechamberlwitfi re-J spect to fiuid in the other chambempowerimeans separate and distinct from said .pressurelequalizlin; means for periodically compressing van'didecompressing the iiuid insaidjoutlet chamber and means for operating: said inlet.,valvemember-and said discharge valve member inhtimed. relationship withsaid power means. 5L A device ior the recovery oi pressure .energy. of fluids processedunder, h h Pressurea proof. essing v system, the device comprisingen intake chamber having an intake ,port, andi anaoutlet ortle'ading to said system; i ritalze'valve.mea' z'iswv controlling said intake portjgoutleti valve-means i controlling said outlet port an outlet chambenr having an inlet port for admission; Of'flllid from said system, and a discharge port; an inlejtvalve V m b oiw tr dlil le 1 orttasdisohareeq vane membercontrolling said discharge port; pressure equalizing means between said two chambers, including means for sealing fluid in sonar said discharge valve member. l. 7 PAUL KOLLSMANQ'M one chamber with respect to Y fluid theother l chamberg meam for periodically compressing and decompressing the fluid in said outletchan'iber; andmeansoperable in timed relationship with said compressing and decompressing means for operating said inlet valve member and said'dis-' charge valve member.

offluids processed under high pressurein a proc essing-system; the device comprising; an intake chamber having an intake port, and anoutlet port leading to said system; an intake checkvalve controlling said intake port; and outlet check valve controlling said outlet port; an outlet'cham her having an inlet port for admissionof fiuid from said system and a discharge port; an inlet valve member controlling said'inlet port; a dis"-' charge valve member controlling said'disch'arge port; I a. movable'pressure equalizing wa11 between said chambers" sealing one chamber with respect to the other,- butpermitting equalization 'of pres I N sure therebetween; means" for periodically com pressing and decompressing the fluid in said outlet chamber andmeans operable in timed relation- 25 ship with said compressingand decompressing means for operating said inlet valve member and REFERENCES CI' IEDP The following'references are of record in the I filefortm patent: v V K 'UNITED STATES PATENTS Number Name Date 1 1,909,145 Berenbruch May 16, 1933 

